Heat exchangers of known construction consist of tubes or groups of tubes which are embedded into a tube sheet. This tube sheet is made either separately, in which case the tube ends must subsequently be fixed in the tube sheet, or the tube sheet is made during the manufacture of the heat exchanger by injecting a sealing compound between the tube ends. The production of such heat exchangers is expensive, since either the tubes must be inserted into the tube sheet and positioned prior to fastening to the tube sheet, or special devices must be used to maintain the proper distance between the tube ends while the sealing compound (self-curing material or plastic melt) is injected between the tubes.